Acoustic device



April 12, 1932- D. G. BLATTNER ACOUSTIC DEVICE Filed June 25, 1930 2Sheets-Sheet INVENTOR D. G. BLA T7'NER ATTORNEY April 12, 1932. I D. G.BLATTNER I 1,853,955

' ACOUSTIC DEVICE Filed June 25, 1930 2 Sheets-Sheet 2 INVENTOR D. 6.84A TTNER A rromvsr Patented Apr. 12, 1932 UNITED STATES PATENT OFFICEDAVID G. BLATTNER, 01F MOUNTAIN LAKES, NEW JERSEY, ASSIGNOR TO BELLTELE- PHONE LABORATORIES, INCORPORATED, OF NEW YORK, N. Y., ACORPORATION OF NEW ,YORK

ACOUSTIC DEVICE Application filed June 25, 1930, Serial No. 463,597, andin Great Britain February 12, 1930.

This invention relates to acoustic horns, and more specifically to thosehorns which are used as loud speaking units in theatres.

The object of this invention is to provide a compact shallow horncapable of faithfully transmitting sound vibrations at high energylevels and suitable for mounting in relatively narrow spaces, such asbetween the screen and back wall or drops of a theatre stage.

In accordance with this object one embodiment of the inventioncontemplates a sound amplifying horn which divides into two soundpassages just back of the bell portion, each passage extending outwardlyin opposite directions substantially at right angles to a medial planethrough the axis of the bell portion and then curving forwardly through180-toward the plane of the mouth of the bell portion.

I In accordance with another feature the invention provides a horn ofrectangular cross section, the major portion of which consists of twohorizontally disposed equal sound passages symmetrically arranged withrespect to a common bell portion having substantially parallelhorizontal walls and diverging side walls, the distance between theparallel walls being substantially greater than the distance between thediverging Walls at the mouth of the horn in order to provide for a widedistribution of sound waves at substantially all frequencies ofimportance in music and speech.

In one embodiment, a horn in accordance with this invention is sodimensioned that the cross sectional area varies according to theexpotential law, that is, the ratio of the areas at axial points a givendistance apart is the same for all portions of the horn.

In another embodiment, the portions of the divided passage may piercethe side wall of the bell portion on their respective sides and bebrought together inside the bell portion into a single throat whichpierces and extends through the rear of the bell portion.

At the end of the throat portion exterior to ..the horn is mounted thereceiver.

Previous to the invention of the above described horns considerabledifliculty was met the screen thus making it a more convenient unit tohandle.

Referring to the accompanying drawings,

Fig. 1 is a top view of one embodiment of a sound amplifying horn inaccordance with the invention;

Fig. 2 is a partial front view of the sound amplifying horn shown inFig. 1

Fig. 3 is a top view of a modified form of the sound amplifying hornshown in Figs. 1 and 2, partially in cross-section;

Fig. 4 is a partial front view of the sound amplifying horn shown inFig. 3.

Referring particularly to'Figs. 1 and 2, a common bell portion 1 havingsubstantially parallel horizontal walls 2 and diverging side Walls 8 and4 is divided into two sound passages 5 and 6 at the rear of said bellportion. The distance between the parallel walls 2 is substantiallygreater than the distance between the diverging walls 3 and 4 at themouth of the horn in order to provide for a'wide distribution of soundwaves at substantially all frequencies of importance in music andspeech.

The two sound passages 5 and 6 are bent outwardly in opposite directionsjust back of the bell portion at 7 and 8 respectively substantially atright angles to a medial plane through the axis of the bell portion.

Both passages then have a straight portion '9 and 10 respectively whichmay be several spectivel'y which return toward the bell portlon 1 andend near said bell ortion. These latter straight portions 11 an 12respectively may return in a plane parallel to the plane of the mouth ofthe bell portion or as shown in Figure 1, the second 'mentioned bends 13and 14 may be more than 180, in which case, the straight portions 11 and12 would turn in at an angle to the plane of the mouth of the bellportion and the passages 5 and 6 would en near the centers of curvatureof the first mentioned bends 7 and 8. It will be appreciated, therefore,that these straight portions 11 and 12 may be the particularrequirements of the place where the horn is to be used. The sound pas-'v is the same for all sages 5 and 6 are thereafter bent at 27 and 28respectively in a plane at right angles to the general plane in whichtheir axes lie through about or 70, whereafter the passages propereachterminate with a flange 25 and 26' res tively to which may be bolted ahorn t roat 17 and 18 carrying a sound gen.- erating unit (not shown).

From the flanges 25 and 26 the section of the passages 5 and 6 increasesin both their dimensions but in one dimension more rapid- 1 than in theother dimension. The dimens1on of the passages arallel to the plane ofthe mouth of the bel portion and perpendicular to the plane of the axesof the passages becoming considerably greater than the dimension in theFgeneral plane of the axes of thepassages. r'om the point 15 at whlchthe two assages intersect the dimension perpendicu ar to the generalplane of the axes of the passages remains constant until the mouthopening is reached. The other d1mension,hhowever, increases rapidly overthis len j he horn, should be so dimensioned that the cross-sectionalarea varies according to the exponential law, that is, the ratio of theareas at axial points a given distance apart ortions of the horn.

A sound generatlng unit with an appropriate throat may be connected toeach of the two flanges 25' and 26.- Alternatively, divided throats maybe connected to each of the two flanges and any number of receivers maybe used de ending upon the amount of sound energy esired.

The horn ma be made of sections of steel provided with anges of angleiron by which the sections may be bolted together. A'flange 16 of angleiron may be affixed by riveting, welding or the like, to the margin ofthe mouth of the bell portion, thus reinforcing themargin and furnishinga means by which the horn may be mounted to some means of support. Thehorn may be suspended by attachin chains to suitable eye bolts 21, 22,23 an 24 shown on flanges 16, 19 and 20. Damping strips or sheets 29 offlannel or like material may be aflixed by adhesive to the surface ofthe horns where required.

In a modified form of this invention as shown in Figures 3 and 4 thereis provided a bell portion similar to that shown in Figures 1 and 2having substantially arallel horizontal walls" 40 and divergin si ewalls 41 and 42; said bell portion being divided into two sound passages43 and 44 at its rear.

The two sound passages 43 and 44 are bent outwardly in oppositedirections at 45 and 46 respectively just back of the bell portionsubstantially at right 'a'ngles to a medial plane through the axis ofthe bell portion. They then have a straight portion 47 and 48respectively which may be several feet in length, after which straightportion they then curve forward at 49 and 50 respectively throu h 180toward the plane of the mouth of t e bell portion; the radius of thebend being portion and after entering the interior of the bell portionbend inward at 55 and 56 respectively to join in a common portion 57which terminates with a flange 58. Attached to the flange 58 by bolts isa horn throat 59 which pierces and extends horizontally through the rearof the bell portion at 60, the axis of said throat portion lyingsubstantiall in a medial plane through the axis of the bell portion. Onemerging from the rear of the bell portion the throat portion 59 is thenbent upward through 90 at 61 in a plane at right angles to the generalplane in which the axes of the sound passages 43 and 44 lie and extendsupward in a straight portion 62 which lies between the front and rearofthe horn in a space formed by the curvature of the first mentioned bends45 and 46 of the sound pas sages 43 and 44 respectively. At the end ofthe ,throat portion exterior to the horn is mounted a sound unit (notshown).

The horn may be made of wood, steel or any other desirable material.Suitable eye bolts 63, 64, 65 and 66 maybe attached at various placeswith which to suspend the horn.

It will be appreciated that many modifications of the above forms shownmay be made without departing from the scope of the invention.

What is claimed is: 1. A horn comprising a bell portion having inlet andoutlet openings, two sound passages communicating with said inletopening, said passages extending laterally in opposite dithroat and bellportions and having two similar looped sound passages of rectangularcross section and rigidly secured to said bell portion, each of saidlooped sound passages extending in opposite directions at right anglesto a medial plane through the axis of the bell portion.

3. A horn comprising a bell portion, two looped sound passagescommunicating with the rear of said bell portion, said passages piercingopposite walls of said bell portion and a throat portion common to saidsound passages extending through the rear of said bell portion.

4. A horn comprising a bell portion of rectangular cross section, twosimilar sound passages of rectangular cross section communicating withthe rear of said bell portion and rigidly secured thereto. said soundpassages extending outwardly in opposite directions at right angles tothe vertical medial plane through said bell portion and curving forwardthrough an angle of 180, the length of said sound passages beingsubstantially greater than the length of said bell portion.

5. A horn comprising a bell portion of rectangular crosssection, thehorizontal dimensionof the mouth of said bell portion beingsubstantially less than its vertical dimension and two conduits curvinghorizontally through 90 from the back of said bell and extending inopposite directions, said conduits having rectangular cross sections,the vertical dimensions of which increase rapidly, their horizontaldimensions increasing only slightly toward the bell portion whereby thesound wave expansion is substantially all in the vertical dimension inthe conduits and greater in the horizontal dimension than in thevertical dimensions in the bell.

6. A horn comprising a bell portion of rectangular cross section havingopposite parallel walls and opposite diverging walls, a pair of similarrectangular sound conduits communicating with the rear of said bellportion and extending in opposite directions between the projectedplanesof the parallel walls of said bell portion, then curving forwardlythrough 180 and continuing for a substantial distance toward said bellportion, said conduits each having a length substantiallv greater thanthe length of said bell portion, and a taper such that the ratio of theareas at axial points a given distance apart is the same for allportions of the horn. 7. A horn comprising a bifurcated sound passage,branches thereof extending in alignment in opposite directions, thencurving forwardly through an angle of 180 and extending toward eachother for a substantial distance and terminating on opposite sides of aportion of the sound passage.

8. A horn comprising a bell portion and two reversely curved conduitscommunicating with the rear of said bell portion and symmetricallydisposed on each side thereof, a substantial portion of each of saidconduits lying between the planes of front and rear of said bell portionand the areas of the sound passage increasing at a rate such that theratio of the areas at axial points a given d stance apart is the samefor-all portions of the horn.

9. A horn comprising two similar reversely curved conduits ofrectangular cross-section having slightly diverging side walls aboutwhich said conduits are curved and widely diverging upper and lowerwalls, said walls defining openings lying in the same plane, the outerwalls meeting at a common edge, said conduits being symmetricallydisposed with respect to a plane bisector of the angle formed by saidjoining walls.

10. A horn comprising two'similar reversely curved conduits ofrectangular cross section having slightly diverging side walls aboutwhich said conduits are curved and widely diverging upper and lowerwalls, said walls defining openings lying in the same plane, the outerwalls meeting at a common edge. said conduits being symmetricallydisposed with respect to a plane bisector of the angle formed by saidjoining walls, and a bell portion having diverging vertical walls forming continuation of the inner walls respec tively of said conduits andparallel horizontal walls one forming a continuation of both upper wallsand the other a continuation of both lower walls of said conduits.

'11. A horn compris ng a bell portion of rectangular cross sectionhaving parallel horizontal walls, diverging vertical walls, two similarrectangular conduits communieating with the rear of said bell portion,the sum of the areas of openings in said conduits beingsubstantially-equal to the cross sectional area of the rear of the bellportion, each of said conduits having a 90 bend in opposite directionsimmediately adjacent the rear side of the outlet openin of said bellportion, said last mentioned nd being of such radiusthat said soundpassages do not intersect the plane of the mouth of the bell portion.13. A horn comprising a bell portion having inlet and outlet opemngs,two sound passages communicating with said inlet openings, said passagesextending laterally in opposite directions at right angles to a medialplane through the axis of the bell portion and curving forward throughan angle of 4 plane through the axis of the ing, said passages beingmore than 180 at a substantial distance from each side of'the outletopening of said bell portion and continuing for a substantial distancetoward said bell portion in such manner that a vertical plane throughthe axis of said portion is atan angle to the plane of the mouth of thebell portion.

14. A horn comprising a bell portion having inlet and outlet opemngs,two sound passages communicating with said inlet openbent outwardly inopposite directions just ack of said bell portion substantially at rightan les to a medial ell portion and curving forward through an angle ofmore than 180 at a substantial distance from each side of the outletopening of said bell portion and continuing toward said bell ortion,said second mentioned bend being 0 such curvature that said passagesterminate near the centers of curvature of said first mentionedv saidbell portion said second mentioned bend being of such radl bends.

15. A horn comprising a bell portion having inlet and outlet openings,two sound passages communicating with said inlet opening, said passagesbeing bent horizontally. outward in opposite directions just back ofsaid bell portion substantially at right an les to a medial lane throu hthe axis of the 11 portion an curving forward through an angle of morethan 180 at a substantial disreasons of said bell portion, said p a: 1t: extending laterally in. o posite dlrections at right angles to a meial plane through the axis of the bell portion and curvin forwardthroughan angle of 180 at a su tantial distance tance'from each side ofthe outlet opening.

of said bell portion and continuing toward 'usthat said sound passagesdo not intersect the plane of the mouth of the bell portion and of suchan angle that said sound passages terminate near the centers ofcurvature of said first mentionedbends.

16. A horn comprisin a bell portion, two

- sound assages commumcating with the rear 7 of sai bell portion, saidsoundpassages extendin in o pos'ite directions to a dlstance from t e meial plane throu h said bell por- I 'tion substantially greater t an theoverall depth of the horn, then curving forward through an angle of 180andretur min to reunite in a common throat within said all portion, theaxis of said throat and said bell portion being substantiallycoincident.

- 17. A'horn comprising a bellportion, two

sound passages commumcating with the rear

